1. Field of Invention
The present invention relates to communications networks and more particularly to the use of a high-speed RF link for a multi-user meeting.
2. Description of Related Art
Digital projectors are becoming increasingly popular for use in business meetings. Typically, a single user connects his notebook or laptop computer, micro-laptop, or possibly an appliance such as a PDA (Personal Digital Assistant) to the digital projector by means of a cable, and the transmission is carried out using the VGA graphics electrical format. This VGA format is analog in nature and carries the equivalent of many Gbits/sec of digital information since the - signal is uncompressed and therefore must communicate the full screen information (e.g., x-dim/pixel1/2*y-dim/pixel1/2*˜24 color bits/pixel*60/sec refresh rate). For pixel dimensions of 640×480 and a refresh rate of 60 Hz, this leads to a transmission requirement of 640*480*24*60=˜500 Mbits/sec. For pixel dimensions of 1024×1280 and a refresh rate of 72 Hz, the transmission rate is ˜2.3 Gbits/sec.
Thus, the bandwidth currently required for connecting a user to a digital projector is quite high (e.g., over 1 Gbit/sec). However, the material generally presented (e.g., PowerPoint™ slides) may be transported in compressed form (e.g., object form) with high fidelity at lesser speeds (e.g., 10 to 100 Mbits/sec). Current approaches to a multi-user meeting with a digital projector do not incorporate application-sensitive bandwidth reduction by transmitting image data in its original object form and then converting the object data into a raster scanned digital image at the projector itself. Likewise, these approaches do not facilitate high-speed communication between multiple users and between a user and an external network.
In addition to the VGA standard, newer interface standards such as DVI (Digital Visual Interface) are becoming increasingly popular. The DVI standard, as popularized by Silicon Image, Intel, and others, has been standardized by the Digital Display Working Group (DDWG) to replace VGA for connections to digital projectors and flat panel displays. This interface consists of a cable comprising three data lines, each running at a rate over 1 Gbit/sec, plus a clock line for synchronization. Alternative standards for digital serial links have also been proposed.
According to either the VGA standard or the DVI standard, each user typically must communicate with the projector via a wired connection such as a cable. This connection requires the user be near the cable, and it limits the number of participants that can simultaneously use the projector, to typically one user. Such a wired connection has the further disadvantages of being by nature susceptible to a faulty physical connection, requiring considerable time to set up, and requiring a semi-skilled individual to make such connection.
Further, this wired arrangement limits the ability of the conferees who desire to communicate digitally with each other because they must resort to the use of floppy disks. In the case of Palm Pilot and other modern PDA's, inter-user communication may be accomplished by means of point-to-point infrared links, but such links are unreliable due to pointing accuracy and line-of-sight obstructions and are also limited in bandwidth. Further, this wired arrangement does not allow more than two conferees to communicate simultaneously and does not allow the conferees to communicate with fixed wired networks such as the local LAN or the Internet.
Emerging standards for wireless connections have also been limited. Bluetooth is an RF format that is designed to allow multiple users with portable machines such as PDA's or laptops to connect to each other or to multiple others on an ad-hoc basis. Such a network is limited in performance to less than 1 Mbit/sec bandwidth for each connection. This data rate is inadequate for conveying complex PowerPoint™ slides rapidly, and is completely inadequate for conveying future presentations that include video and audio information. Further, if multiple users share a Bluetooth channel, their individual data channels will be limited to much less than 1 Mbit/sec.
Thus, the bandwidth currently required for connecting a user to a digital projector creates challenges for both wireline and wireless systems, and current approaches typically do not facilitate high-speed transfer of graphics data over such a connection. Likewise, current approaches do not facilitate high-speed communication between multiple users or between a user and an external network.